c-如何打印/检查浮点寄存器

Question

假设我有以下内容：

c: .float 3.14
movss c(%rip), %xmm0

如何以可读的方式检查该寄存器？例如，我可以获得整个调试输出，但不仅仅是一个友好的数字：

>>> p/f $xmm0
$2 = {
v4_float = {[0] = 3.1400001, [1.40129846e-45] = 0, [2.80259693e-45] = 0, [4.20389539e-45] = 0},
v2_double = {[0] = 5.3286132608536752e-315, [1.40129846e-45] = 0},
v16_int8 = {[0] = -61, [1.40129846e-45] = -11, [2.80259693e-45] = 72, [4.20389539e-45] = 64, [5.60519386e-45] = 0 <repeats 12 times>},
v8_int16 = {[0] = -2621, [1.40129846e-45] = 16456, [2.80259693e-45] = 0, [4.20389539e-45] = 0, [5.60519386e-45] = 0, [7.00649232e-45] = 0, [8.40779079e-45] = 0, [9.80908925e-45] = 0},
v4_int32 = {[0] = 3.1400001, [1.40129846e-45] = 0, [2.80259693e-45] = 0, [4.20389539e-45] = 0},
v2_int64 = {[0] = 5.3286132608536752e-315, [1.40129846e-45] = 0},
uint128 = 3.93143274128552720884e-4942
}

在没有所有其他输出行的情况下，我如何获得值3.14？

希望我能从检查变量本身中得到一些类似的东西：

>>> x/f &c
0x6000df:   3.1400001

Answer 1

您可以使用点符号来打印特定项目。例如，要打印float和double值：

>>> p $xmm0.v4_float[0]
$4 = 3.1400001
>>> p $xmm0.v2_double[0]
$5 = 5.3286132608536752e-315

显然，double在这里是没有意义的，但用来表明v4_float、v2_double、v16_int8、。。。应该起作用。